Objective: To identify teenager's knowledge of transmission and prevention of sexually transmitted diseases (STD). Methods: A sample of children and teenagers aged between 10 and 19 years participated in the study. Data were collected through a structured questionnaire developed for the study. Results: The findings suggested that the main source of information on Sexually Transmitted Diseases was the participants' school teacher. Sexually transmitted diseases are not entirely unknown by the participants in the study, with AIDS the most notorious.